One of the not so publicised benefits of optimisers/micro inverters is that they allow you to have mismatched panels on the same string which is great for phased expansion of a system. We have 310 and 320 watt panels on one string and 335 and 405 watt panels on a second string with the smaller panels not affecting the output from the larger panels.

23 minutes ago, Nickfromwales said:

I've not got any direct experience with Victron, but unless you have optimisers you cannot find a dead panel without checking each one. We've installed systems with optimisers (Tigo) for yonks without any issues whatsoever, quite the opposite tbh.

ah, yep that would be impossible for me to track without microinverters or optimisers indeed.